A bearing assembly of the above-described type is described in EP 1 744 071 A2. It is envisaged here to position the bearing in an exact position relative the bearing carrier. For this purpose it is provided to inject a plastic material between the bearing ring comprised of steel and the bearing carrier also comprised of steel or steel plate; the plastic material ensures the precise relative position.
It is generally probably also possible to envisage a manufacturing of a bearing carrier entirely out of plastic. Either thermosets or thermoplastics alternatively come into question as plastics.
As is well known, thermoplastics are such plastics that can be thermoplastically deformed in a certain temperature range. This process is reversible. Thermoplastics differ from thermosets in this way. Thermosets, meanwhile, are plastics that can no longer be deformed after their curing. Thermosets are hard polymer materials that are three-dimensionally cross-linked by chemical primary valence bonding.
Thermosets thus have no heating range, i.e., even with a temperature increase the material retains its rigidity and has a low thermal expansion that leads to a high dimensional stability. In contrast, thermoplastics lose their rigidity properties with heating; technically undesirable dimensional changes result.
Therefore manufacturing bearing carriers or bearing covers from a thermoplastic brings disadvantages with heating due to the temperature sensitivity or the loss of rigidity as well as disadvantageous dimensional changes. However, bearing carriers or bearing covers made from a thermoset must disadvantageously be mechanically reworked after the injecting, for example for the providing of a bearing seat, for which purpose a precision-turning- or grinding-process is required. Alternatively steel rings as bearing seats can be injected or overmolded, which, however, must in turn be partly reworked. With both variants the outer rings of the bearing must then be mounted in the thermoset cover directly or in the steel ring, for example, using a press-fit. Another axial securing of the outer ring of the rolling-element bearing is also necessary in part, for example, by snap rings.
In principle with the injection-molding manufacturing of bearing carriers or covers from a thermoset, higher temperatures and longer dwell times are required than with thermoplastic injection-molding. If a rolling-element bearing is to be directly overmolded with thermosetting plastic, there is therefore the danger that structural changes arise in the rolling-element bearing rings of the bearing and thus the properties of the bearing are significantly worsened.
Thus both solutions—the use of a thermoplastic and of a thermoset for the base material for a bearing carrier or a cover element—have respective advantages and disadvantages.